Hydraulic valve lifter



1.. J. VAN SLOOTEN HYDRAULIC VALVE LIFTER March 25, 1958 Filed May 14,1956 INVENTOR. 01121; v! [fan 5100;? MC? ATTORNE K United ratesHYDRAULIC VALVE LIFTER Louis J. Van Slooten, Holland, Mich., assignor toGeneral Motors Corporation, Detroit, Mich a corporation of DelawareApplication May 14,1956, Serial No. 584,561

4 Claims. (Cl. 12390) its upper end by a piston or plungertelescopically slidable and supported therein on a column of oil orother incompressible fluid confined in the bottom of the cylinder. Thecylinder is slidably supported in the engine frame for longitudinallyreciprocable movement in following one of the lobes on the cam shaft,the piston moving therewith under the action of the oil column andeffecting through suitable linkage a corresponding movement of theengine valve which is biased to closed position by a relatively stiffspring. The piston is provided with a passage extending longitudinallytherethrough which is closable by a check valve sensitive to pressurewithin the chamber below the piston but which opens upon removal of thatpressure to permit a flow of oil into the chamber from a reservoir abovethe piston, thereby tending to keep the pressure chamber filled at alltimes. A light spring is provided to bias the piston upwardly in thecylinder end thereby expanding the adjuster to take up the valve lashduring the interval between lifting strokes when the engine valve isunstressed. Such lash adjusters when used in internal combustion enginevalve trains which include valves normally urged closed by relativelystifI' valve springs are subject to what is known as valve lifterpump-up, particularly during so-called valve spring surge.

Valve spring surge is a term used to describe high frequencyless-than-normal oscillatory movements of the valve springs which occurat certain engine speeds usually spaced by definite increments in anengine-speed scale.

One of the results of valve spring surge is to increase the amount oflash in the valve train. To compensate for this increase in lash thelash adjuster pumps-up, i. e., the spring of the adjuster furtherseparates the cylinder and piston to increase the column of oil actingtherebetween. If, for example, the engine speed is passing through avalve spring surge range to perhaps a higher speed range where therewill be no valve spring surge and the lash adjusters are pumped-up tocompensate for the increased lash caused by the surge the valves will nolonger seat, resulting in severe losses of engine power as well as otherextremely undesirable conditions such as valve burning, etc.

It is therefore an object of this invention to delay pump-up of suchlash adjusters during valve spring surge so that the ranges of enginespeeds at which valve spring surge" occurs may be passed through withoutlash adjuster pump-up occurring under such conditions.

It is a further object of this invention to provide means for delayinglash adjuster pump-up so that it occurs at atent Patented Mar. as, was

higher engine speeds than would otherwise be the case without suchmeans.

For a clearer understanding of the invention and the objects thereof,the invention will now be described in detail with reference to theaccompanying drawing, in which:

' Figure l is a transverse sectional view through a porion of aninternal combustion engine Whose valve-operating train includes ahydraulic valve lifter incorporating the novel means for delayingpump-up of the lash adjuster in accordance with the invention; and,

Figure 2 is an enlarged fragmentary view of the engine and the hydraulicvalve lifter of Figure 1 showing the parts in greater detail.

Referring now to the drawing, in Figure 1 the engine is illustrated ashaving a cylinder block and crankcase 1 in which a power piston 2operates in a cylinder 3. The numeral 4 designates the engine cylinderhead in which is reciprocably mounted a poppet valve 5 biased to itsclosed position by a returnspring 6 and movable in the opening directionbya cylinder head mounted valve rocker 7 in response to upward movementof a push rod 8 operatively connecting the push rod to an engine-drivencam 9 through a hydraulic lash adjuster or valve lifter 10.

The valve lifter 10, as best seen in Figure 2 comprises a pair oftelescopically slidable cup-shaped members 11 and 12. The outer member12 has its bottom end resting on the operating surface of the cam 9 andforms a cylinder in which the inner member 11 constitutes a piston orplunger. Within the cylinder 12 below the plunger 11 is an oil cushionchamber 13 in which a body of incompressible fluid is contained. In theparticular arrangement illustrated this fluid is oil which is suppliedfrom the engine-lubricating system by an oil gallery 14 in the blockcommunicating with the bore 15 in which the cylinder is slidablyreciprocable. The oil delivered by the gallery 14 to the bore 15 passesthrough the side Walls of the plunger and cylinder via the cylinderexternal groove 16 and cylinder and plunger ports Hand 18, respectively,into the reservoir 19 formed by the hollow interior of the Plunger 11.This supply of oil to the reservoir is for the purpose of replenishingthat which is regularly lost from the chamber 13 during operation byleakage between the plunger and cylinder side walls with each liftstroke of the cam 9 in opening the engine valve 5. A passage 21extending through the bottom of the cup-shaped plunger serves to connectthe reservoir 19 and the cushioning chamber 13 for this purpose. Toinsure against backflow through passage 21 during the lift stroke thereis provided a check valve in the form of a ball 22 which is retained inproximity to the lower port of passage 21 by a small retaining cup 20. Aplunger spring 23 is also placed in the chamber 13 to effectre-lengthening of the lifter 10 through successive lift strokes of thecam 9 and further serves to maintain the ball check valve cup 20 inplace against the bottom of piston or plunger 11. During each intervalbetween lift strokes the engine valve 5 is closed and the plunger spring23 acts against plunger 11 to take up clearance or lash between it andthe engine valve, while causing the lifter cylinder to remain in contactwith the operating surface of the cam. In so doing, and immediately uponclosure of the engine valve 5, the lifter cylinder moves downward towardthe cam axis relative to the lifter plunger 11 and effects anenlargement of the oil cushion chamber 13, producing a consequent dropin pressure therein and unseating of the check valve 22.

With the structure so far described if the engine speed should be suchthat the valve spring 6 is surging, valve 5 will tend not to seatthereby increasing the lash in the valve train between the cam 9 and therocker 7 engaging the stern of valve 5. As a result of this increase inlash the spring 23 will act against the plunger '11 to take up of thevalve train as to maintainth'e valve off its seat throughout entireengine cycles. This, of course, results in a severe loss of power whichmay even prevent further acceleration of the engine. If the speed rangeat which the valve spring surge occurs should also happen to be therange in which, say, a shift in an automatic transmission is normallymade, such sur e and pump-tip may prevent the shift from taki'nglpla'cedue to the loss of power and inability of the engine to furtheraccelerate. To alleviate this Condition and prevent its occurrence, thepresent invention has been proposed which upon reference to Figure .2primarily comprises in s'e'ftiii'g resilient means (in this instance inthe form of a helical'coil spring 24) between the cylinder and thepiston which yieldingly opposes the action of spring 23 tending to causepumpup. The usual hydraulic lifter normally includes a plug 25 closingthe upper end of the piston 11 and a retaining ring 26" which holds theplug and the piston in the cyiim,

der 12 and more or less maintains the valve lifter assembly intact.Spring 24, then, as shown by Figure 2, is positioned so as to abut 'theretaining ring 26 at its upperend and the upper side of the plug 25 atits lower end which in turn rests against the upper end of the piston11. The characteristic of the spring 24 is such that it yieldinglyopposes the action of spring 23, i. e'., spring 23' is somewhat stifferthan spring 24.

The efiect of. spring 24', then, is to ofie'r increasing re sistance tothe action of spring 23 as valve lifter pum up begins to take place. Byproper selection of the characteristic'of spring 24 pump-up can beretarded or delayed so as to allow the engine to pass through the rangesof engine speed at which valve spring fsurgefoc' curs before valvelifter pump-up takes place. The springs 23 and 24 preload each other tosome extent in their initial state. When valve spring surge'occurs inthe valve train it causes the lower spring and thelifter to expandupward to take up the clearance in the valve train caused by valvespring surge. Due to the lower spring expanding it begins to lose itsinitial load while the upper spring is being compressed and its load isincreased. Be-

cause of these opposing spring forces the lifter assembly] will reactslower in taking up valve train clearance when valve spring surgeoccurs. Due to the slower reaction asaaesv continue to seat at properintervals in the engine cycle throughout the speed range of the engineresulting in better engine performance.

I claim:

1. A hydraulic valve lifter having a cylinder with a slidably fittedpiston defining an oil cushion chamber and an oil reservoir thereinbelow and above the piston respectively, said piston having .a passagefor flow of oil from said reservoir to said chamber, a check valveadapted to prevent reverse flow through said passage;

resilient means acting between said piston and cylinder'to urge itsmovement within the cylinder in the directionto enlarge said chamber,and resilient means acting between said piston and cylinder opposingsaid movement.

2. In a hydraulic lash adjuster having two telescopioally associatedmembers in thrust-transmitting relation with a body of fluidtherebetween and a check valve controlling a passage in one of saidmembers communicating with said body, resilient means acting betweensaid members urging movement of said members to increase the spacetherebetween wherein said body is located and further resilient meansacting between said members ieldi'ngiy opposing such movement. I

3 A hydraulic tappet comprisinga cylinder having one end closed and theother open, a piston in the cylinder defining an on cushion chamber andan oil reservoir therein below and above the piston respectively, afirst spring act-ing' between said piston and cylinder normally urgingthe piston out of the cylinder, said piston having a passage connectingthe chamber and reservoir on opposite sides of the piston, a non-returnvalve permitting flow into the chamber beneath the piston, and a secondspring acting between said piston and cylinder tending to ur e thepistoninto the cylinder, said first spring effecting a greater initialbiasing on said, piston than said second spring.

4. In a valve train including a valve and spring therefor, a hydraulicvalve lifter having'means tending to re taid pump-up of said lifterduring surge of said valve spring comprising a cylinder having one endclosed and the other open, a piston in the cylinder defining an oilcushion chamber and an oil reservoir therein below and above the pistonrespectively, a first spring in said chamher acting between said pistonand cylinder normally urging the piston out of the cylinder, saidpistonhaving a passage connecting the chamber and reservoir on oppositesides of the piston, a non-return valve preventing flow into the chamberbeneath the'piston, retaining means in the open end of the-cylinder-above the piston preventing its removal from the cylinder, anda second spring between thepiston and the retaining means yielding'lyopposing the action of said first spring.

References Cited in the file of this patent UNITED STATES PATENTS2,595,583 Johnson May 6, 1952 2,746,437 .Vaii Slooten May 22, 19562,761,433 Kilgoie Sept. 4, 1956

